According to an article in 'The Atlantic' by Kate Julian last month, there is a revolution in sexual activity in the US - and it's not just there, but across the Western world too. In her piece, 'The Sex Recession', she points out that young, and not so young, men and women are foregoing sexual intercourse.

According to an article in 'The Atlantic' by Kate Julian last month, there is a revolution in sexual activity in the US - and it's not just there, but across the Western world too. In her piece, 'The Sex Recession', she points out that young, and not so young, men and women are foregoing sexual intercourse.

On the face of it, this should be a boom time for sex, since contraceptives are available extensively and if these fail, so too is abortion.

Hook-ups are continuously invited online (I've had three pop-ups while writing this paragraph, from Illiana, who likes me) and every kind of taste can be catered for almost instantly by downloading Grindr or Tinder.

Polyamory is a household word, sexting no longer raises an eyebrow, twerking is a showpiece for stage and threesomes are de rigueur. In this country, the Union of Students in Ireland placed a list of hints on its website about this, as if it was the acceptable norm.

The worried conservative elders of yesteryear predicted chaos in family life if the permissive trend continued, with broken marriages, children abandoned without fathers, rocketing sexually transmitted diseases and associated infertility and untrammelled abortion.

On the other side of the divide, liberals believed sexual nirvana would be reached when the sexual act and procreation were uncoupled.

Sexual fulfilment would inevitably follow and relationships between the sexes would be egalitarian once the patriarchy was jettisoned.

Both were wrong, according to Julian. The sex recession has descended upon America.

From 1991 to 2017, the Centres for Disease Control and Prevention's youth risk behaviour survey found the percentage of high-school students who had intercourse dropped from 54 to 40. So in the course of a generation, sexual activity changed from something that most teens engaged in to one that most didn't.

Similarly, the General Social Survey of 2016 reported a decline in sexual activity among adults in general; even since 2016 it appears to have further accelerated according to Jean Twenge, a professor of psychology at San Diego State University.

These studies show young adults in their twenties are having sex less frequently and are more likely to be celibate than Boomers or Generation X. They are likely to have fewer lifetime sexual partners.

The teenage pregnancy rate has also declined sharply and the abortion rate in the US is at its lowest since Roe v Wade (1972), which led to the federal liberalisation of abortion.

And it is not just in the US this is happening, although it is more pronounced there. Other counties are reporting similar trends including Britain's National Survey of Sexual Attitudes and Lifestyles, Finland's Finsex study and data from the Netherlands and Sweden.

Japan poses the biggest demographic crisis. In 2005, a third of Japanese single people aged between 18 and 34 were virgins; by 2015, 43pc were, and the share who said they did not intend to get married had risen. Among the married population, 47pc had not had sex in at least a month.

The obvious question is - why? Are young people more virtuous and abstaining for moral reasons; are they more focused on their studies than on finding sexual and romantic partners; are they impressed that a life of sexual exploitation is one of emptiness; does porn provide a better and less demanding out?

The answer is elusive but there are a number of reasons that have been suggested. The obvious one is the near ubiquitous availability of porn, which can satisfy the basic sexual needs of those who view it. Whether it is addictive or not is a question not yet settled but it is used by many people instead of person-to-person sex.

Another possibility is that the use of social media is so time consuming it intrudes upon time available for sexual pursuits.

Some evidence of this comes from a study in the 'Journal of Population Economics' that examined the introduction of broadband internet in the US on a county-by-county basis and found its arrival explained 7pc to 13pc of the teen-birth-rate decline from 1999 to 2007.

Moreover, the incessant use of social media may inhibit personal growth and developing the skills to form close relationships.

It may also be that women feel more empowered to say "no" to unwanted sex, as the aggression of feminism has grown, with "toxic masculinity" targeted as never before.

These questions are of more than journalistic interest, since they may have implication for behaviour in other countries.

If the Summer of Love was the beginning of a cultural change that swept all before it for four decades, then a Sexual Recession, theoretically, could do the same. If relationships are not formed, then populations will dwindle and economies will suffer.

The 1960s was feared for what it might and did bring in the sphere of relationships and sexuality. Wouldn't it be ironic if the upshot of this was sexual continence spreading across the liberated West for reasons we might not wish?

Ultimately, the trend may be part of the cycle of behaviour, a pendulum swinging in a particular direction, prompted by recently emerging social habits. Perhaps we are witnessing what Shakespeare observed: "There is a tide in the affairs of men."